Posted: 12/06/2013 at 22:03
Achieving an environmental balance is not necessarily going to come easy or cheap, and when you create imbalance by growing things under glass, pest infestations are often a consequence. If you are happy to spend money to overcome the problem, introduce some predators:
There are a number of online suppliers. One alternative is to spend several hours a day manually removing them (eg squashing and washing off etc) but you can only keep the infestation under control doing this, not eliminate it. A second alternative is to make your own natural pesticides by extracting natural poisons from plants and spraying them with it. Oxalic acid from rhubarb leaves, Nicotine from Nicotiana tabacum (the actual tobacco plant), for example.